The use of (p, X) spectrometry for hair analysis presents difficulties if absolute elemental concentrations are required. This arises because it is not clear what mass of hair the beam is hitting. Attempts to get around this by measuring the scattered protons, or the intensity of the sulphur X-ray peak, or by calculation, were not successful. Neither of the parameters was related to the mass analysed, because of probable irregular shape and elemental distribution. The problems can be overcome by dissolving a weighed amount of hair in hot nitric acid, adding an internal standard, and drying it on filter paper or a thin plastic film.